Presentation for NTVA Contents Background Technology / Systems - PowerPoint PPT Presentation

Presentation for NTVA

Contents • Background • Technology / Systems • Method and features • Test results • Prospects 2

Background - Historical SI (SINTEF) developed FSM • – After the Alexander Kielland accident in 1980 Hårek Hognestad at SI develops the Field Signature Method (FSM) for crack monitoring − CorrOcean got the rights to FSM in 1988 SINTEF SI develops transient potential drop method • (Transient Potential Drop) – Based on the FSM method – For determination of stress in steel – Tested for monitoring of stress in railway rail (neutral temperature in CWR (Continuous Welded Rail) In 2005 Ferrx acquired rights and test equipment • from SINTEF SI – Ferrx founded based on development and industrialization of this patented method. 3 Ferrx 3 3

SI’s test in sea at Nutec 1986 Objective: Crack Detection in T-joint weld Supported by Norsk Hydro, Statoil, Norweld Measurements were influenced by stress Excitation and material changes before cracks were visible. In the beginning they were regarded as disturbing signals, however, it was soon assumed that they were related to stress and material changes. Sensing Pins Excitation 4 Ferrx 4

Background – Market Mostly defined by participating oil companies The aging and life extension of steel structures is a major challenge in • many industry sectors. A safe permissible extension of structural life for continuing production • and service will generate considerable savings for industry and society. FEMM provides accurate data for the assessment of structural integrity • and improves prediction of remaining life of structures and life extension optimization. Application examples from the O&G market: • Monitoring of critical points of structure e.g. welds in steel risers or – well head pipes. Degree of strain damage for pipelines during pipe laying. – Verify correctness of formulas based on empirical data. – 5

System monitoring railway rail Field Trial 2009/2010 . To monitor Stress related to Rail’s Neutral Temperature and to demonstrate the reliability of the instrumentation system. Main System Specification: • Autonomous operation • 1 - 4 measurements per day • Communication via mobile network to Internet server • Solar cell based power supply 6 6

Monitoring of Subsea Pipes DEMO2000 2010-2013 (RCN, Shell, Dong, Lundin) FMC WOR System on work over riser. Designed for water depth down to 1500m 7 Ferrx

Monitoring corrosion in pipes One system monitoring 3 pipes, GSM online to server. Installation of system in client’s workshop before sending to the field location 8

FEMM instrumentation SI: 28 pin-pairs (4 sets of pins and excitation) Up to 8 SIs on the SI Bus => 224 pairs/system. Pin matrix customized Sensor Interface Data for actual defect SI bus Acquisition Unit Communication connector Connection points protected before encapsulation Dedicated FEMM SW Different encapsulation, Prototype Subsea same electronics datalogger on 8” riser pipe 9

Monitoring Capabilities ▪ Relative stresses • Elastic stress • Detection of plasticity, stress exceeding yield • Changes of residual stresses ▪ Remanent stress (max stress since last measurement) ▪ Fatigue development due to cyclic loads • Material deterioration (dislocations and surface microcracks) ▪ Crack initiation and growth/size estimation • Distinguishes between internal and external cracks. ▪ Non-intrusive monitoring of internal erosion and corrosion ▪ Monitoring of outer surface corrosion 10

FEMM sensor on steel structure Monitored steel structure • A and B are current excitation connections • C and D make a sensing pin-pair. Typically 28 pin- pairs on pipe’s butt -weld • Connections made by soldering, or stud-welding or spring-loaded sensing pins Sensors have same operational lifetime as monitored structures • The area covered by sensing pins is monitored • 11 11

Method description Transient Potential Drop (patented) Excitation Current and Voltage Response Excitation current Relative measurements. Deviation between two different response signals: d(t) =[n(t) / i(t) - 1]1000 (ppt) t Typ 0,5sec, Response Signals Timeconstant: Deviation d(t) Т ≈ ¼ a 2 σ μ a = wall thickness σ = elect. conductivity d(t) n(t) μ = magnet. permeability n(t) > i(t) i(t) DC t t Response signals (transients) Increased permeability for measurements i(t) and n(t) due to tension stress DC ≡ DCPD (=FSM) 12

Typical deviation curves Shape of curves influenced by µ, σ , depth and w.t. Increased compression stress. Crack in the outer surface. Crack or metal loss on the => Reduced permeability => Mainly increased inside of pipe wall.  Increased resistance resistance (crack and corrosion are distinguished by data analysis) 13

Fatigue of metals Stress amplitude Monitored Bulk resistance Permeability Surface resistance parameters Load cycles N Fatigue process’ 3 phases and changing parameters monitored by FEMM 14

Example of fatigue testing Run at Marintek in Trondheim T-joint in test rig Instrumentation on a Monitoring weld in single weld toe. OD=8’’ WOR pipe Zoom at the saddle point 15

Monitoring Hi-Cycle Fatigue Tests of riser pipes at Marintek (DEMO2000) Test pipe (FMC WOR): • Outer Diameter = 8’’ • Wall thickness = 15,5mm • Yield ≥ 758MPa • Weld monitored Monitoring of: • Changes in Residual stresses • Material changes due to cyclic loads • Crack initiation 4-point bending down . • Crack growth Pipe in test rig, one-sided loading. Highest tension stress at 6 o’clock 16 16

Monitored riser pipe fatigue Measured at 6 o’clock at the point of highest tension stress. Typical change of electrical impedance in outer surface of weld during material deterioration and crack initiation. Sample 12640 deviation 20 15 10 Increase of Crack growth dislocation Increase of microcracks in surface Deviation(ppt) 5 monitoring density 0 Visible Crack Visible Crack -5 18280 Crack Detected -10 -15 Decrease of Increase of resistance dominates permeability -20 0 0.5 1 1.5 2 2.5 dominates Nr. Cycles 4 # Load cycles x 10 17 17

Pipe weld fatigue parameters. All 28 sensing pin pairs on the complete circumference. Surface material deterioration, estimated Estimated decrease of permeability . increase of resistance in 1mm surface layer ppt ppt Bulk resistance Crack size growth ppt ppt 18

Recognizing 60 to 70 percent of total lifetime of welds Deviation at 4 x DC Marintek welded riser pipe 5 A fresh material will first go through shakedown/hardening effects, followed Deviation samples 10490-10650 by a steady decrease as the dislocation 0 density increases, then an increase as the crack forms and finally a notable -5 decrease as the crack starts growing Riser pipe with weld into the material. This final effect tends to occur at about 60-70% of lifetime. -10 0 0.5 1 1.5 2 2.5 3 3.5 Nr cycles (breakdown at around 37000 cycles) 4 x 10 Deviation at 4 x DC Marintek T-Joint West Side Deviation at 4 x DC Marintek gusset weld South 0 30 Deviation DCcomp samples 10469-10537 -10 25 Gusset plate weld Deviation DCcomp -20 20 samples 97-118 T-joint weld -30 15 -40 10 -50 5 -60 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 1 2 3 4 5 6 7 8 9 Nr cycles (breakdown at about 5000 cycles) Nr cycles (breakdown at about 93500) 4 x 10 19

Detection of creep in HAZ for Tepco Test in Ferrx lab 2010 7 specimens, 6 with different degrees of creep Creep area marked with blue dotted line W=20, T=15 Pin holder: 3 pin pairs, 10mm spacing 20 20

FEMM IT for onsite riser inspection Sensors installed on most exposed locations e.g. 3 riser joints. Certified in 2016 by DNV GL according to DNV-RP-A203 Sensor on weld Instrumented 8” pipe Portable Instrument FEMM PC SW for analyzing data Pressure compensated CE marked • NDT of riser joint: Removeable • Change of residual stress • Certified for Ex Zone 1 • Material degradation • Crack initiation and growth • Internal metal loss • 21 21

Prospect: ROV retrofit NDT clamp ROV “pinholder” based on Deepwater’s Retroclamp Specifications: ▪ Most pipe diameters ▪ Pins can penetrate coating ▪ Instantaneous measurement ▪ Deviation measurements using fixed autonomous system 22 22